A part of the background hereof lies in the development of light emitters based on direct bandgap semiconductors such as III-V semiconductors. Such devices, including light emitting diodes and laser diodes, are in widespread commercial use.
Another part of the background hereof lies in the development of wide bandgap semiconductors to achieve high minority carrier injection efficiency in a device known as a heterojunction bipolar transistor (HBT), which was first proposed in 1948 (see e.g. U.S. Pat. No. 2,569,376; see also H. Kroemer, “Theory Of A Wide-Gap Emitter For Transistors” Proceedings Of The IRE, 45, 1535-1544 (1957)). These transistor devices are capable of operation at extremely high speeds. An InP HBT has been demonstrated to exhibit operation at a speed above 500 GHz (see W. Hafez, J. W. Lai, and M. Feng, Elec Lett. 39, 1475 (October 2003). In the parent Application hereof (the above-referenced copending U.S. patent application Ser. No. 11/068,561), very short laser pulses are produced by switching a heterojunction bipolar transistor laser back and forth between a stimulated emission mode that produces laser pulses, and a spontaneous emission mode.
It is among the objects of the present invention to produce heterojunction bipolar transistor lasers and techniques that are capable of advantageous signal processing to obtain a variety of selected optical outputs, including wave mixing modulation laser transistors and techniques.